Trimethylsiloxysilicate is an MQ-type silicone resin that has found assorted uses in personal care products. Two commercially available MQ resins are Silicone SR 1000, from Momentive Performance Materials, and MQ-1600 from Dow Corning. According to some suppliers, trimethylsiloxysilicate may be dissolved in different organic and silicone oils up to concentrations of 50% or more, and is compatible with various types of personal care ingredients, including certain silicones, alcohols, esters and hydrocarbons. The material is hydrophobic, having a reported water contact angle of about 105.8° at standard temperature and pressure. This ingredient offers strong cohesion that may be used to confer transfer resistance and wash-off resistance. The material has film forming and sebum absorption capabilities, and has been used to improve sunscreen products. As a viscosity enhancer, trimethylsiloxysilicate resin has been used to improve the stability of lipsticks and emulsions.
Nevertheless, one significant drawback of pure trimethylsiloxysilicate resin is the difficulty of incorporating the resin into an internal phase of oil and water emulsion systems. Emulsification of up to 3% resin may have been achieved to date, but, to the best of our knowledge, nothing like the much higher concentrations (i.e. 10% to 45% or more) described herein, and especially in systems that are long term stable and suitable for topical application. To the best of the applicant's knowledge, no such emulsion systems existed prior to the present invention.
Another drawback of the material is the brittleness of the film that is formed. If the film is deposited on a non-rigid surface that is subject to change shape (i.e. hair, face, hands, etc.), then the film is likely to crack, flake or peel, thereby compromising product efficacy and providing a user with a poor aesthetic experience.
The ability of a liquid to spread over a surface is governed by relative surface energies. More wetting and more adhesion are achieved when the difference between the surface energies of the two phases are nearly identical. On the other hand, the larger the surface tension of the liquid compared to the surface energy of the solid, the less wetting that occurs. The surface of healthy human hair is coated with fatty acid lipid, making it negatively charged and hydrophobic. Surface energies of healthy hair have been reported to be about 24-28 dynes/cm, while the surface tension of water at 25° C. is about 72 dynes/cm. As a result, the contact angle between healthy hair and water has been reported to be about 103°±4°, with Asian and African hair averaging slightly less than Caucasian hair. Thus, healthy hair is designed to repel water.
In contrast, it is well known that the shaft of the hair may become damaged as a result of over-exposure to chemical agents (as in style and color treatments), mechanical stress (i.e. from combing) and heat (i.e. from blow drying and curling irons). Such overexposure may compromise the protective cuticle layer of the hair fiber, exposing the cortex to further damage. The damage may manifest as a split in the hair shaft that extends from the free end of the hair fiber back toward the scalp. The surface energy of damaged hair may be taken to be about 30-50 dynes/cm, compared to 24-28 dynes/cm for more healthy hair. As a result, damaged hair is significantly less hydrophobic than healthy hair. In fact, many commercial treatments are so harmful, that the hair is rendered somewhat hydrophilic (i.e. water-hair contact angles of 50°-80° have been reported).
A commercially available product line called Nexxus ProMend, from Alberto-Culver, is reported to bind split ends. The products use a polymer solution complex of Polyquaternium 28 (a copolymer of vinylpyrolidone and methacrylaminopropyl trimethylammonium chloride) and PVM/MA copolymer (a copolymer of methyl vinyl ether and maleic anhydride). Our testing showed that after one rinse, Nexxus ProMend products retained only 30 to 60% mending of split ends. To the best of our knowledge, no commercially available product retains at least 75% mending after a minimum of three rinses.